1. Field of the Invention
The present invention relates to signal storing circuits and devices related thereto, more specifically to the signal storing circuits and devices related thereto using ferroelectrics.
2. Description of the Related Art
IC-cards are used for credit cards and for identification tags in distributing systems. Recently, IC-cards mounting logic LSIs (large scale integrated circuit) thereon as well as installing micro-computers therein are commercially available. A circuit shown in FIG. 26 is known as a sequence logic processing circuit used for the logic LSIs and the microcomputers.
The logic processing circuit 2 shown in FIG. 26 comprises a combined logic block CB including NAND circuits and/or OR circuits and a latching block LT latching an output of the combined logic block CB. The combined logic block CB performs a predetermined logic operation to an input data IN provided thereto, and outputs a resulting data OUT therefrom. The latching block LT latches the resulting data OUT at the positive edge (Low-to-high transition) or the negative edge (High-to-low transition) of a clock pulse Cp. The data OUT thus latched therein is outputted as an output data Q.
With the logic processing circuit 2, the data OUT latched can be outputted within a duration equivalent to a time period in which upcoming clock pulse Cp is detected by latching the data OUT at the positive edge (or negative edge) of the clock pulse Cp. In this way, a stable output can be obtained by eliminating noises from the resulting data.
Sequential processing having a high reliability and other related using a combination of a plurality of the logic processing circuits 2 can perform processing.
The conventional processing circuit 2 described above, however, has the following problems to be solved. An adequate voltage must be applied to the circuit 2 all the time in order to hold the data being processed.
Data being processed under sequential processing and that stored in a memory are completely erased when the power supply is shut off by an accident. The data can not be recovered even after the recovery of the power supply. In order to recover the data into the original one just before the accident, another sequential processing must be performed all over again from its beginning. It consumes much time to perform the sequential processing for every accident, and the data erase cause serious damages on the reliability in processing.
The power supply would be in unstablized when the circuit is used for a non-contact type IC card because the power is supplied thereto through radio waves. Suspension in the power supply makes the processing difficult especially when a greater amount of data need to be processed under the real-time basis.
In order to suppress the power consumption of the circuit, a low-power consumption type-latching block LT shown in FIG. 27 is proposed. This is achieved by utilizing transistor(s) having a high threshold voltage, which lower the power consumption.
A circuit 4 having a low threshold voltage comprises inverter circuits INV0 and INV1 both including low threshold transistors, which can operate fast in operating speed but consume much power. A circuit 6 having a high threshold voltage, on the contrary, comprises inverter circuits inverter circuits INV2 and INV3 both including high threshold transistors which are operated slowly in operating speed but consume not much power.
A power control part 8 supplies the power to the circuit 4 when the circuit 2 is in operation, and the control part 8 suspends the power supply to the circuit 4 when the circuit 2 is in stand-by State. In this way, the resulting data OUT is outputted through the inverter circuits INV0 and INV1 both can operate fast in operating speed during the operating-State, and the data OUT is stored in the inverter circuits INV2 and INV3 both consumes not much power during the stand-by State. It is, therefore, preferred for the circuit 2 to store the data OUT in such a way.
Although, the low-power consumption type-latching block LT shown in FIG. 27 during the Stand-by State consumes a relatively smaller power, it still consumes the power.